Question 1

Which experiment provided definitive evidence that DNA, and not protein, is the hereditary material in phages?

Accepted Answer

Hershey and Chase's experiment using radioactive sulfur and phosphorus

Question 2

According to Chargaff's rules, which of the following equations correctly represents the relationship between purines and pyrimidines in double-stranded DNA?

Accepted Answer

$$[A] + [G] = [C] + [T]$$

Question 3

Which feature of DNA structure ensures that the molecule has a uniform width, as revealed by X-ray diffraction studies?

Accepted Answer

Pairing of purine with pyrimidine

Question 4

During DNA replication, which enzyme is responsible for relieving strain ahead of the replication fork by breaking, swiveling, and rejoining parental DNA?

Accepted Answer

Topoisomerase

Question 5

In the Hershey-Chase experiment, why was radioactive phosphorus ($$^{32}P) $$used to label DNA?

Accepted Answer

Phosphorus is found in DNA but not in protein

Question 6

Which of the following best describes the antiparallel nature of DNA strands?

Accepted Answer

One strand runs 5' to 3', the other runs 3' to 5'

Question 7

Which enzyme synthesizes a short RNA primer during DNA replication?

Accepted Answer

Primase

Question 8

What is the direction of DNA synthesis by DNA polymerase?

Accepted Answer

5' to 3' direction

Question 9

A mutation in the gene encoding a mismatch repair enzyme can lead to which medical condition due to accumulation of DNA errors?

Accepted Answer

Colon cancer

Question 10

Which of the following correctly describes the process of excision repair for thymine dimers caused by UV exposure?

Accepted Answer

Nuclease removes the damaged section, DNA polymerase fills in nucleotides, and DNA ligase seals the strand

Question 11

Which of the following statements about telomeres is correct?

Accepted Answer

Telomeres postpone the shortening of DNA molecules but do not prevent it

Question 12

Which base pairs are formed in DNA, and how many hydrogen bonds stabilize each pair?

Accepted Answer

Adenine pairs with thymine (2 bonds); guanine pairs with cytosine (3 bonds)

Question 13

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule contains one parental strand and one newly synthesized strand

Question 14

What is the role of single-strand binding proteins during DNA replication?

Accepted Answer

They stabilize unwound parental DNA strands

Question 15

Which of the following is a correct sequence of events during lagging strand synthesis?

Accepted Answer

Primase synthesizes RNA primer, DNA polymerase III extends Okazaki fragment, DNA polymerase I replaces RNA primer, DNA ligase joins fragments

Question 16

If a DNA molecule has 20% adenine, what percentage of guanine would you expect according to Chargaff's rules?

Accepted Answer

30%

Question 17

Which scientist(s) used X-ray diffraction to provide evidence for the double helix structure of DNA?

Accepted Answer

Rosalind Franklin and Maurice Wilkins

Question 18

Which of the following is NOT a component of a DNA nucleotide?

Accepted Answer

Ribose sugar

Question 19

What is the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments by forming phosphodiester bonds

Question 20

Which of the following best describes the role of DNA polymerase during DNA replication?

Accepted Answer

It adds nucleotides to the 3' end of a growing DNA strand

Chapter 16: The Molecular Basis of Inheritance – DNA Structure and Replication

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